Boat propeller



y 1962 o. BIHLMIRE 3,033,293

BOAT PROPELLER Filed Oct. 20, 1958 INVENTOR.

OTTO L. BIHLMIRE T TORNEY United States Patent Ofifice 3,033,293 Patented May 8, 1962 3,033,23 BOAT PROPELLER Otto L. Bihlmire, Servi Corporation, Constantine, Mich. Filed Oct. 20, 1958, Ser. No. 768,099 4 Claims. (Cl. 170159) automatically to varying conditions under which the boats are operated.

Another object of the invention is to provide a boat propeller which will not become bent, nicked nor dented as easily as the conventional propellers presently being used as standard equipment on small motors and boats.

Still another object of the invention is to provide a durable, unbreakable propeller which will withstand attack from salt water and abrasion from entrained foreign materials in the water.

A further object is to provide a rugged boat propeller requiring a minimum amount of service and having a long life under all normal operating conditions and treatment.

Another object of the invention is to provide a boat propeller having a plurality of blades which yield under pressure created by high power output of the boat motor, to change the pitch thereof, and which return fully to original position when the pressure is relieved.

Another object is to provide a composition for a propeller imparting thereto the foregoing characteristics.

Additional objects and advantages of the present invention will become apparent from the following description and the accompanying drawing, therein:

FIGURE 1 is a rear elevational view of my propeller constructed of special propeller composition;

FIGURE 2 is a side elevational view of the propeller shown in FIGURE 1;

FIGURES 3 and 4 are enlarged cross sectional views of one of the propeller blades, taken on lines 3-3 and 4-4, respectively, of FIGURE 1.

Referring more specifically to the drawing, numeral designates a propeller for a conventional outboard motor having three blades 12, 12' and 12 of substantial pitch and with a plurality of reinforcing ribs 14 on the forward surface 16 of each blade, the rear surface 17 being smooth and unobstructed. The blades are formed integrally with a hub 18 of the same material which preferably is provided with a bushing or sleeve 20 which slips onto and firmly grips the drive shaft from the motor. A hole 22 is provided in the rear end of the hub and. bushing for the usual shear pin. For the purpose of the present invention the particular design and detailed construction of the propeller may be considered as conventional and the one described herein is for the purpose of illustration. The propellers to which the invention is applicable may vary in size over a wide range and may have two, three or more blades. They may be smooth on the forward surface as well as on the rear surface, and the shape, pitch and construction of the blades may vary from one propeller to another.

The present invention is primarily concerned with boat propellers constructed of a nylon base material impregnated with fibre-glass throughout both the hub and blades, as illustrated by the small curved lines'30 shown on the surface of the views in the four figures of the drawings. The amount of fibre-glass intermixed with the nylon has been found to be a rather narrow critical range falling between about fifteen percent (15%) and thirty percent (30%) by weight with the optimum properties being present in nylon base propellers impregnated with approximately eighteen to twenty-five percent (l8%-25%) of fibre-glass by weight.

glass provides a propeller having all the desirable properties and characteristics. It has been found that nylon propellers impregnated with less than about fifteen percent (15%) have suflicient strength but the moisture absorption and flexibility are too high for satisfactory performance and durability. Nylon base material with thirty percent (30%) and over while having acceptable water absorption characteristics is too rigid and susceptible to breakage from sudden impact. the propeller blades constructed of a nylon base with over about thirty percent (30%) is insuflicient for satisfactory performance of the present propeller. Percentages of fibre-glass between about ten and forty-five percent (1()%-45%) will give some of the desirable properties and characteristics, including varying degrees of water absorption, flexibility and ductility; however, percentages less than about fifteen percent and more than about thirty percent do not give satisfactory degrees for all the desired properties. The moisture absorption of the nylon decreases with an increase of fibre-glass impregnation, thus increasing the life of the propeller under normal operating condition. However, as the fibre-glass is increased above about thirty percent the flexibility is too low and the brittleness too high to permit the propeller to perform and last satisfactorily.

One of the important features of the present boat propeller constructed of nylon and fibre-glass in amounts between about fifteen and thirty percent, is its ability to automatically vary the pitch of the blades with variations in power output of the motor, particularly at the high power output encountered in starting and rapid acceleration. When the propeller is placed under high torque output during starting and high power output, the blades flex, turning slightly throughout their length from the forward edge to the rear edge and reducing the effective pitch of the blades. The degree of flexibility of the blades is highly critical since no significant variation in pitch is desriable during normal cluising or gradual acceleration in the cruising range. Immediate and substantially complete return of the blades to their original pitch takes place when the boat reaches the desired speed and the torque resistance on the propeller is diminished to that present in the normal cruising range. The blades constructed of the present nylon-fibre-glass material can be subjected to repeated pitch variations without losing their ability to return fully to their original pitch. The variable pitch characteristics of the present integral blade and hub propeller construction are not found in either metal propellers, the blades of which are rigid and when distorted remain in the deformed condition, or rubber, the blades of which are inherently so flexible that they distort during normal cruising of the boat and power output of the motor.

The present propellers are molded from the nylonfibre-glass material using standard materials readily available on the market, and molds in convential plastic fabricating equipment. The propellers formed of nylon impregnated with fifteen to thirty percent by weight of fibre-glass have in addition to the variable pitch characteristics excellent resistance to chemicals and foreign matter in water normally causing severe corrosion and disintegration of metal propellers, and will resist bumps, shock and impact from foreign objects, and consequently will not become nicked, scratched or broken as readily as the conventional metal propellers.

A specific composition of nylon 1 impregnated with twenty percent (20%) by weight fibre- The flexibility of V In the foregoing description of a specific example of the present invention, only nylon and fibre-glass have been referred to as the materials from which my propeller is made. However other plastic and fibrous materials can be used which provide at least some of the durable characteristics of the nylon-fibre-glass material.

While a number of variations in my propeller have been mentioned herein, other changes and modifications can be made without departing from the scope of the present invention.

I claim:

1. A flexible boat propeller adapted to operate fully submerged in water, consisting essentially of a nylon base material having about twenty percent by weight of fibreglass thoroughly dispersed therein.

2. A flexible boat propeller adapted to operate fully submerged in water, consisting essentially of a nylon base material having thoroughly dispersed therein between about eighteen to twenty-five percent by weight of fibreglass.

3. A flexible boat propeller adapted to operate fully submerged in water, composed of a nylon base having between about fifteen to thirty percent by weight of fibreglass dispersed therein.

4. A flexible boat propeller adapted to operated fully submerged in water, composed of a nylon base having between ten and forty-five percent by weight of fibre-glass dispersed therein.

References Cited in the file of this patent UNITED STATES PATENTS 1,002,796 Antoni Sept. 5, 1911 1,463,153 Clay July 31, 1923 1,847,666 Persons Mar. 1, 1932 2,032,224 Paton Feb. 25, 1936 2,446,119 White July 27, 1948 2,473,665 Van Nort June 21, 1949 2,498,348 Thompson Feb. 21, 1950 2,659,444 Stanley Nov. 17, 1953 2,874,139 Symons Feb. 17, 1959 FOREIGN PATENTS 596,636 Great Britain Jan. 8, 1948 

